The effects of hormones on skin can be complex and difficult to diagnose. The thyroid gland, pituitary gland, adrenal glands, testicles, and ovaries all produce hormones which if excessive (hyper), deficient (hypo), or out of balance produce changes in the skin and hair. The characteristics of all hormonal skin problems are: loss of hair in an evenly distributed pattern on each side of the body, darkening of the skin, no pruritis (itching) and a chronic duration. The skin changes are just one symptom of hormonal abnormalities; other body systems are also affected and the signs related to these may be more diagnostic than the skin changes.
The most frequently encountered skin problems in male dogs related to sex hormones is the overproduction of estrogen (female hormone), which causes feminization of the dog. One cause is a tumor of the testicles, called Sertoli cell tumor; in other cases the testicles appear normal and the cause is unknown. Signs include loss of hair, particularly on the flanks and in the genital area; mammary gland enlargement and sometimes milk production; lack of libido; attractiveness to other male dogs; darkening and thickening of the skin; oiliness of the skin; and excessive wax in the ears. If the cause is from a tumor, the affected testicle will be enlarged, but often the testicle is retained to the abdomen and cannot be seen. Castration is recommended, particularly if a tumor is suspected. A replacement testosterone injection may be given. Medicated shampoos and ear cleaning will help improve the skin and ear condition. Corticosteroids can be used as an alternative to castration if the cause is not from a tumor and, in some cases, may be required following castration.
Hyperestrogenism is the production of too much estrogen in the female dog, and is most commonly due to cysts on the ovaries.2 Symptoms include loss of hair on the flanks an genital areas, and later on the abdomen and under the elbows. The skin darkens, becomes oily, and the ears produce excessive wax. Infertility, false pregnancy, and enlargement of the vulva and mammary glands with milk production are other common symptoms. Treatment is best performed with ovariohysterectomy (spay). Medicated shampoos and ear treatment are also recommended. The prognosis is good in the majority of cases and response is seen about three weeks of surgery.
Estrogens used for therapeutic purposes or estrogen sources such as Sertoli cell or ovarian granulosa cell tumors may cause bone marrow toxicity in dogs. The condition is characterized by hematologic abnormalities including thrombocytopenia (deficiency of platelets in the blood; this causes bleeding into the tissues, bruising, and slow blood clotting after injury), anemia (a deficiency of red cells or of hemoglobin in the blood), and leukocytosis (an increase in the number of white cells in the blood) or leukopenia (a reduction in the number of white cells in the blood, typical of various diseases). Despite intensive therapy with blood or platelet-rich transfusions, broad-spectrum antibiotics, steroids, and bone marrow stimulants, prognosis is unfavorable.1
Golden retriever, a dog breed predisposed to testicular tumors
Hypoestrogenism is a condition caused by too low production of estrogen and is seen most often in dogs which have been spayed. There is a gradual loss and thinning of the hair starting in the genital and lower abdominal areas, and eventually spreading to the chest, neck, and ears. The skin is soft and smooth, and the coat is very fine. The nipples and vulva are small, and there may be dribbling of urine. Replacement synthetic female hormones usually reverses the symptoms, although they may need to be given for a number of months before a response is noted.
- Estrogen-induced myelotoxicity in dogs: A review (2015)
- Profiles of Steroid Hormones in Canine X-Linked Muscular Dystrophy via Stable Isotope Dilution LC-MS/MS (2015)
- Canine testicular tumors: two types of seminomas can be differentiated by immunohistochemistry (2015)